Heretofore, two kinds of magnetic heads have been proposed for perpendicular recording. One type of head uses auxiliary magnetic pole excitation as shown in FIG. 1 and the other type of head uses main magnetic pole excitation as shown in FIG. 2.
With either kind of head, it is required that a main magnetic pole 1 be close to or in contact with a perpendicular magnetization film 2 which constitutes a recording film. In the case of perpendicular recording, the proximity of the perpendicular magnetization film 2 to the main magnetic pole 1 creates a strong interaction, permitting recording on and reading of the recording film. (See Technical Report of IECE of Japan (1979).)
The flow of magnetic flux produced using a auxiliary magnetic pole exitation type of head during recording is shown in FIG. 3, where the vicinity of the auxiliary magnetic pole 5 is schematically shown. The direction in which the recording film is moved is indicated by arrow 7. The magnetic flux convergies through internal magnetization film 3 to join around the front end of the main magnetic pole 1 thus recording on or reading the portions of the perpendicular magnetization film 2 lying closest to the front end. It is to be noted that the auxiliary magnetic pole 5 is located remotely from the recording film and that the magnetic flux density at its surface is small. Therefore, it is impossible to record or read information by using the auxiliary magnetic pole alone. Also shown in FIGS. 1-3 the substrate 4 for supporting a magnetic medium, and a coil 6.
A conventional magnetic head for recording information on both sides of a magnetic medium utilizing this perpendicular magnetic recording is shown in FIG. 4. This head is of the auxiliary magnetic pole excitation kind, and acts in such a way that information is written to, or read from, recording films 2-(1) and 3-(1) by the use of a main magnetic pole 1-(1), an auxiliary magnetic pole 5-(1), and a read/write coil 6-(1). When information is written to or read from the recording films 2-(2) and 3-(2), another main magnetic pole 1-(2), another auxiliary magnetic pole 5-(2), and another read/write coil 6-(2) are used. During these operations, it is unlikely that the recording films 2-(2) and 3-(2) will be overwritten by the magnetic field set up by the auxiliary magnetic pole 5-(1) or that information will be transferred from the recording films 2-(2) and 3-(2) to the auxiliary magnetic pole 5-(1), because perpendicular recording intrinsically relies on the interaction caused by proximity. The same situation applies to the auxiliary magnetic pole 5-(2) and the recording films 2-(1) and 3-(1).
The conventional structure as shown in FIG. 4 has as many as four magnetic poles 1-(1), 1-(2), 5-(1), and 5-(2) which are all required to be located relatively close to the magnetic medium. Accordingly, the head is very difficult to machine. Generally, magnetic heads utilizing vertical recording produce lower output signal levels than annular internal recording heads. To increase the output levels, the number of turns in the coil 6 is increased which consequently increase the volume occupied by the coil. This makes it difficult to manufacture the head compactly. In particular, each coil is wound on an auxiliary magnetic pole and so it is impossible to make the space between the auxiliary magnetic pole and the neighboring main magnetic pole less than the thickness of the wound coil. Hence, miniaturization of the head is difficult to attain. This difficulty also arises even if the recording film, which is the combination of the vertical magnetization film and the internal magnetization film as shown in FIGS. 1-4, is replaced by a single-layer film consisting only of a perpendicular magnetization film. Also, when four magnetic poles are provided, the magnetic recorder requires additional parts for precisely locating the recording medium and the four magnetic poles relative to each other.